Many industrial reactions are carried out in a mixing tank type reactor using solid catalyst slurry. These reactions are carried out by contacting a reactive gas, for example, hydrogen, ammonia or the like, with liquid in the presence of the catalyst. After the reaction is finished, generally the catalyst is removed by filtration to collect the reaction product.
However, a slurried catalyst has problems in safety, increase in waste material, operability and productivity. For example, there are problems that many of catalysts are spontaneously combustible, so powder and slurry catalysts must be handled with care, and the catalyst must be removed by filtration etc. in order to collect the reaction product, thus leading to complex facilities and operation.
As a process that requires neither a mixing operation by stirring or gas bubbling nor filtration separation of a catalyst, there can be mentioned a fixed-bed system. As to forms of a catalyst for use in the fixed-bed system, a molded catalyst of a pellet shape, noodle shape, or tablet shape has been well known conventionally. By subjecting powdery material having a catalyst activity to molding processing by such method as compression or extrusion into the above-mentioned form, a construction having an infinite number of fine pores therein is formed thereby satisfying both of the catalyst configuration and great surface area. For example, such technique is disclosed in JP-A 6-211754.
According to the reaction system, such problem as handleability of the catalyst and waste material can be solved, but there are many reactions to which the system can not be applied. For example, there were cases where temperature control was troublesome in reactions accompanied with absorption or generation of heat, and uneven liquid-gas distribution in a reactor sometimes resulted in an insufficient reaction percentage or many side reactions caused by local concentration gradient.
In tertiary amination reaction, when trying to obtain a reaction product at a high reaction percentage using the molded catalyst described in JP-A 6-211754, undesirable byproducts are generated in not small amounts. The byproduct includes not only wax or an aldol condensate generated by a side reaction of alcohol as the raw material, but also a tertiary amine generated as byproduct from ammonia, primary or secondary amine due to disproportionation of primary or secondary amine. Although various improvements have been carried out for practicing the technique highly selectively by suppressing formation of such byproducts, it has been difficult to practice this reaction highly selectively by an easy process.
JP-A 2003-176255 discloses a reactor in which a catalyst metal is adhered on the surface of monolith. It is noted that this reactor has an advantage that in a hydrogenation reaction between a gas and liquid, mass transfer is accelerated compared with a fixed-bed packed reactor of a conventional type, because the pressure drop of the reactor is small and the velocity of the gas and liquid can be made large.
JP-A 2002-35569 discloses a method of gas/liquid reaction in which a liquid and gas are fed as a liquid/gas mixture from a tank to a monolith catalyst reactor and then a reaction product drawn from the outlet is circulated in a tank. Reaction raw materials and reactants can be heated and cooled separately from the catalyst, and thus there are noted advantages such as minimization of byproduct formation and of catalyst inactivation.